New API for getting uids have specific permissions from SystemConfig

SysetmConfig is internal service for frameworks only which cannot
use by Connectivity mainline module, but PermissionMonitor which
is part of the module needs to get uids that have been granted
INTERNET/UPDATE_DEVICE_STATS permission from SystemConfig.
Therefore, add a new API to SystemConfigManager that can get
these uids from SysetmConfig.

Bug: 177188455
Test: atest SystemConfigTest
Change-Id: I62bdd969b1b813631ed6223df97bda21a39aec2c